A traffic collision, also known as a traffic accident, motor vehicle collision, motor vehicle accident, car accident, automobile accident, Road Traffic Collision (RTC) or car crash, occurs when a vehicle collides with another vehicle, pedestrian, animal, road debris, or other stationary obstruction, such as a tree or utility pole. Traffic collisions may result in injury, death and property damage.

A number of factors contribute to the risk of collision including; vehicle design, speed of operation, road design, road environment, driver skill and/or impairment and driver behaviour. Worldwide motor vehicle collisions lead to death and disability as well as financial costs to both society and the individuals involved.

Terminology

Many different terms are commonly used to describe vehicle collisions. The World Health Organization use the term road traffic injury,[1] while the U.S. Census Bureau uses the term motor vehicle accidents (MVA)[2] and Transport Canada uses the term "motor vehicle traffic collision" (MVTC).[3] Other terms that are commonly used include auto accident, car accident, car crash, car smash, car wreck, motor vehicle collision (MVC), personal injury collision (PIC), road accident, road traffic accident (RTA), road traffic collision (RTC), road traffic incident (RTI), road traffic accident and later road traffic collision, as well as more unofficial terms including smash-up and fender bender.

Traffic collision

Some organizations have begun to avoid the term "accident". Although auto collisions are rare in terms of the number of vehicles on the road and the distance they travel, addressing the contributing factors can reduce their likelihood. For example, proper signage can decrease driver error and thereby reduce crash frequency by a third or more.[4] That is why these organizations prefer the term "collision" rather than "accident".

However, treating collisions as anything other than "accidents" has been criticized for holding back safety improvements, because a culture of blame may discourage the involved parties from fully disclosing the facts, and thus frustrate attempts to address the real root causes.[5]

Other common types of Virginia DMV reportable crashes include those crashes which begin on a public highway with a vehicle loss of control and end upon private property.

Causes

Driver factors

57%

27%

Roadway
factors

6%

3%

3%

1%

2%

Vehicle factors

Breakdown of British and
American crash causes

A 1985 study by K. Rumar, using British and American crash reports as data, found that 57% of crashes were due solely to driver factors, 27% to combined roadway and driver factors, 6% to combined vehicle and driver factors, 3% solely to roadway factors, 3% to combined roadway, driver, and vehicle factors, 2% solely to vehicle factors and 1% to combined roadway and vehicle factors.[6]

Human factors

Human factors in vehicle collisions include all factors related to drivers and other road users that may contribute to a collision. Examples include driver behavior, visual and auditory acuity, decision-making ability, and reaction speed.

A 1985 report based on British and American crash data found driver error, intoxication and other human factors contribute wholly or partly to about 93% of crashes.[6]

An RAC survey of British drivers found that most thought they were better than average drivers; a contradictory result showing overconfidence in their abilities. Nearly all drivers who had been in a crash did not believe themselves to be at fault.[7] One survey of drivers reported that they thought the key elements of good driving were:[8]

controlling a car including a good awareness of the car's size and capabilities

reading and reacting to road conditions, weather, road signs and the environment

alertness, reading and anticipating the behaviour of other drivers.

Although proficiency in these skills is taught and tested as part of the driving exam, a 'good' driver can still be at a high risk of crashing because:

...the feeling of being confident in more and more challenging situations is experienced as evidence of driving ability, and that 'proven' ability reinforces the feelings of confidence. Confidence feeds itself and grows unchecked until something happens – a near-miss or an accident.[8]

An AXA survey concluded Irish drivers are very safety-conscious relative to other European drivers. However, this does not translate to significantly lower crash rates in Ireland.[9]

Accompanying changes to road designs have been wide-scale adoptions of rules of the road alongside law enforcement policies that included drink-driving laws, setting of speed limits, and speed enforcement systems such as speed cameras. Some countries' driving tests have been expanded to test a new driver's behavior during emergencies, and their hazard perception.

There are demographic differences in crash rates. For example, although young people tend to have good reaction times, disproportionately more young male drivers feature in accidents,[10] with researchers observing that many exhibit behaviors and attitudes to risk that can place them in more hazardous situations than other road users.[8] This is reflected by actuaries when they set insurance rates for different age groups, partly based on their age, sex, and choice of vehicle. Older drivers with slower reactions might be expected to be involved in more accidents, but this has not been the case as they tend to drive less and, apparently, more cautiously.[11] Attempts to impose traffic policies can be complicated by local circumstances and driver behaviour. In 1969 Leeming warned that there is a balance to be struck when "improving" the safety of a road:[12]

Many places that look dangerous have few or no accidents. Conversely, a location that does not look dangerous may have a high crash frequency. This is, in part, because if drivers perceive a location as hazardous, they take more care. Accidents may be more likely to happen when hazardous road or traffic conditions are not obvious at a glance, or where the conditions are too complicated for the limited human machine to perceive and react in the time and distance available. (This fact can be used to improve safety, by putting up signs in accident-prone locations, like ones stated above.)

This phenomenon has been observed in risk compensation research, where the predicted reductions in accident rates have not occurred after legislative or technical changes. One study observed that the introduction of improved brakes resulted in more aggressive driving,[13] and another argued that compulsory seat belt laws have not been accompanied by a clearly attributed fall in overall fatalities.[14]

In the 1990s Hans Monderman's studies of driver behavior led him to the realization that signs and regulations had an adverse effect on a driver's ability to interact safely with other road users. Monderman developed shared space principles, rooted in the principles of the woonerven of the 1970s. He found that the removal of highway clutter, while allowing drivers and other road users to mingle with equal priority, could help drivers recognize environmental clues. They relied on their cognitive skills alone, reducing traffic speeds radically and resulting in lower levels of road casualties and lower levels of congestion.[15]

Some crashes are intended, staged crashes, for example, involve at least one party who hopes to crash a vehicle in order to submit lucrative claims to an insurance company. [16] Latin immigrants in the 1990s were recruited to drive cars that were meant to be crashed. It was an illegal and risky job, for which they would be paid only $100. Jose Luis Lopez Perez, a staged crash driver, died after one such maneuver, leading to an investigation which uncovered the increasing frequency of this type of crash.[17]

Motor vehicle speed

The U.S. Department of Transportation's Federal Highway Administration review research on traffic speed in 1998.[18] The summary states:

That the evidence shows that the risk of having a crash is increased both for vehicles traveling slower than the average speed, and for those traveling above the average speed.

That the risk of being injured increases exponentially with speeds much faster than the median speed.

That the severity of a crash depends on the vehicle speed change at impact.

That there is limited evidence that suggests that lower speed limits result in lower speeds on a system wide basis.

That most crashes related to speed involve speed too fast for the conditions.

That more research is needed to determine the effectiveness of traffic calming.

The Road and Traffic Authority (RTA) of the Australian state of New South Wales (NSW) asserts speeding (travelling too fast for the prevailing conditions or above the posted speed limit[19]) is a factor in about 40 percent of road deaths.[20] The RTA also say speeding increases the risk of a crash and its severity.[20] On another webpage, the RTA qualify their claims by referring to one specific piece of research from 1997, and stating "research has shown that the risk of a crash causing death or injury increases rapidly, even with small increases above an appropriately set speed limit."[21]

The contributory factor report in the official British road casualty statistics show for 2006, that "exceeding speed limit" was a contributory factor in 5% of all casualty crashes (14% of all fatal crashes), and that "travelling too fast for conditions" was a contributory factor in 11% of all casualty crashes (18% of all fatal crashes).[22]

Driver impairment

Driver impairment describes factors that prevent the driver from driving at their normal level of skill. Common impairments include:

Insurance statistics demonstrate a notably higher incidence of accidents and fatalities among teenage and early twenty-aged drivers, with insurance rates reflecting this data. Teens and early twenty-aged drivers have the highest incidence of both accidents and fatalities among all driving age groups. This was observed to be true well before the advent of mobile phones. Females in this age group suffer a somewhat lower accident and fatality rate than males but still well above the median across all age groups. Also within this group, the highest accident incidence rate occurs within the first year of licensed driving. For this reason many US states have enacted a zero-tolerance policy wherein receiving a moving violation within the first six months to one year of obtaining a license results in automatic license suspension. No US state allows fourteen year-olds to obtain drivers licenses any longer.

Old age

Old age, with some jurisdictions requiring driver retesting for reaction speed and eyesight after a certain age;

Research suggests that the driver's attention is affected by distracting sounds such as conversations and operating a mobile phone while driving. Many jurisdictions now restrict or outlaw the use of some types of phone within the car. Recent research conducted by British scientists suggests that music can also have an effect; classical music is considered to be calming, yet too much could relax the driver to a condition of distraction. On the other hand, hard rock may encourage the driver to step on the acceleration pedal, thus creating a potentially dangerous situation on the road.[25]

Combinations of factors

Several conditions can work together to create a much worse situation, for example:

Combining low doses of alcohol and cannabis has a more severe effect on driving performance than either cannabis or alcohol in isolation,[26] or

Taking recommended doses of several drugs together, which individually do not cause impairment, may combine to bring on drowsiness or other impairment. This could be more pronounced in an elderly person whose renal function is less efficient than a younger person's.[27]

Thus there are situations when a person may be impaired, but still legally allowed to drive, and becomes a potential hazard to themselves and other road users. Pedestrians or cyclists are affected in the same way and can similarly jeopardize themselves or others when on the road.

Road design

A potential long fall stopped by an early guardrail, ca. 1920. Guardrails, median barriers, or other physical objects can help reduce the consequences of an accident or minimize damage.

A 1985 US study showed that about 34% of serious crashes had contributing factors related to the roadway or its environment. Most of these crashes also involved a human factor.[6] The road or environmental factor was either noted as making a significant contribution to the circumstances of the crash, or did not allow room to recover. In these circumstances it is frequently the driver who is blamed rather than the road; those reporting the accident have a tendency to overlook the human factors involved, such as the subtleties of design and maintenance that a driver could fail to observe or inadequately compensate for.[28]

Research has shown that careful design and maintenance, with well-designed intersections, road surfaces, visibility and traffic control devices, can result in significant improvements in accident rates. Individual roads also have widely differing performance in the event of an impact. In Europe there are now EuroRAP tests that indicate how "self-explaining" and forgiving a particular road and its roadside would be in the event of a major incident.

In the UK, research has shown that investment in a safe road infrastructure programme could yield a ⅓ reduction in road deaths saving as much as £6billion per year.[29] A consortium of 13 major road safety stakeholders have formed the Campaign for Safe Road Design, which is calling on the UK Government to make safe road design a national transport priority.

Vehicle design and maintenance

Research has shown that, across all collision types, it is less likely that seat belts were worn in collisions involving death or serious injury, rather than light injury; wearing a seat belt reduces the risk of death by about two thirds.[30]Seat belt use is controversial, with notable critics such as Professor John Adams suggesting that their use may lead to a net increase in road casualties due to a phenomenon known as risk compensation.[31]

Maintenance

A well-designed and well-maintained vehicle, with good brakes, tires and well-adjusted suspension will be more controllable in an emergency and thus be better equipped to avoid collisions. Some mandatory vehicle inspection schemes include tests for some aspects of roadworthiness, such as the UK's MOT test or German TÜV conformance inspection.

The design of vehicles has also evolved to improve protection after collision, both for vehicle occupants and for those outside of the vehicle. Much of this work was led by automotive industry competition and technological innovation, leading to measures such as Saab's safety cage and reinforced roof pillars of 1946, Ford´s 1956 Lifeguard safety package, and Saab and Volvo's introduction of standard fit seatbelts in 1959. Other initiatives were accelerated as a reaction to consumer pressure, after publications such as Ralph Nader's 1965 book Unsafe at Any Speed accused motor manufacturers of indifference towards safety.

In the early 1970s British Leyland started an intensive programme of vehicle safety research, producing a number of prototype experimental safety vehicles demonstrating various innovations for occupant and pedestrian protection such as: air bags, anti-lock brakes, impact-absorbing side-panels, front and rear head restraints, run-flat tyres, smooth and deformable front-ends, impact-absorbing bumpers, and retractable headlamps.[32] Design has also been influenced by government legislation, such as the Euro NCAPimpact test.

Common features designed to improve safety include: thicker pillars, safety glass, interiors with no sharp edges, stronger bodies, other active or passive safety features, and smooth exteriors to reduce the consequences of an impact with pedestrians.

The UK Department for Transport publish road casualty statistics for each type of collision and vehicle through its Road Casualties Great Britain report.[33] These statistics show a ten to one ratio of in-vehicle fatalities between types of car. In most cars, occupants have a 2–8% chance of death in a two-car collision.

Center of gravity

Some crash types tend to have more serious consequences, Rollovers have become more common in recent years, perhaps due to increased popularity of taller SUVs, people carriers, and minivans, which have a higher center of gravity than standard passenger cars. Rollovers can be fatal, especially if the occupants are ejected because they were not wearing seat belts (83% of ejections during rollovers were fatal when the driver did not wear a seat belt, compared to 25% when they did).[30] After a new design of Mercedes Benz notoriously failed a 'moose test' (sudden swerving to avoid an obstacle), some manufacturers enhance suspension using stability control linked to an anti-lock braking system to reduce the likelihood of rollover. After retrofitting these systems to its models in 1999–2000, Mercedes saw its models involved in fewer crashes[34]

Now about 40% of new US vehicles, mainly the SUVs, vans and pickup trucks that are more susceptible to rollover, are being produced with a lower center of gravity and enhanced suspension with stability control linked to its anti-lock braking system to reduce the risk of rollover and meet US federal requirements that mandate anti-rollover technology by September 2011.[35]

Motorcycles

Motorcyclists have little protection other than their clothing; this difference is reflected in the casualty statistics, where they are more than twice as likely to suffer severely after a collision. In 2005 there were 198,735 road crashes with 271,017 reported casualties on roads in Great Britain. This included 3,201 deaths (1.1%) and 28,954 serious injuries (10.7%) overall. Of these casualties 178,302 (66%) were car users and 24,824 (9%) were motorcyclists, of whom 569 were killed (2.3%) and 5,939 seriously injured (24%).[36]

Prevention

A large body of knowledge has been amassed on how to prevent car crashes, and reduce the severity of those that do occur. See Road Traffic Safety.

United Nations response

Owing to the global and massive scale of the issue, with predictions that by 2020 road traffic deaths and injuries will exceed HIV/AIDS as a burden of death and disability,[37] the United Nations and its subsidiary bodies have passed resolutions and held conferences on the issue. The first United Nations General Assembly resolution and debate was in 2003[38] The World Day of Remembrance for Road Traffic Victims was declared in 2005. In 2009 the first high level ministerial conference on road safety was held in Moscow.

The World Health Organization, a specialized agency of the United Nations Organization, in its Global Status Report on Road Safety 2009, states that over 90% of the world’s fatalities on the roads occur in low-income and middle-income countries, which have only 48% of the world’s registered vehicles, and predicts that road traffic injuries will rise to become the fifth leading cause of death by 2030 [39]

Epidemiology

Main article: Epidemiology of motor vehicle collisions

Deaths for road traffic accidents per 100,000 inhabitants in 2004.[40]

no data

< 5

5-12.5

12.5-20

20-27.5

27.5-35

35-42.5

42.5-50

50-57.5

57.5-65

65-72.5

72.5-80

> 80

Road fatalities per vehicle-km (fatalities per 1 billion km)

no data

< 5.0

5.0-6.5

6.5-8.0

8.0-9.5

9.5-11.0

11.0-12.5

12.5-14.0

14.0-15.5

15.5-17.0

17.0-18.5

18.5-20.0

> 20.0

Worldwide it was estimated in 2004 that 1.2 million people were killed (2.2% of all deaths) and 50 million more were injured in motor vehicle collisions.[1][41] India recorded 105,000 traffic deaths in a year, followed by China with over 96,000 deaths.[42] This makes motor vehicle collisions the leading cause of injury death among children worldwide 10 – 19 years old (260,000 children die a year, 10 million are injured)[43] and the sixth leading preventable cause of death in the United States[44] (45,800 people died and 2.4 million were injured in 2005).[45] In Canada they are the cause of 48% of severe injuries.[46]

Crash rates

The safety performance of roadways are almost always reported as rates. That is, some measure of harm (deaths, injuries, or number of crashes) divided by some measure of exposure to the risk of this harm. Rates are used so the safety performance of different locations can be compared, and to prioritize safety improvements.

Common rates related to road traffic fatalities include the number of deaths per capita, per registered vehicle, per licensed driver, or per vehicle mile or kilometer traveled. Simple counts are almost never used. The annual count of fatalities is a rate, namely, the number of fatalities per year.

There is no one rate that is superior to others in any general sense. The rate to be selected depends on the question being asked – and often also on what data are available. What is important is to specify exactly what rate is measured and how it relates to the problem being addressed. Some agencies concentrate on crashes per total vehicle distance traveled. Others combine rates. The U. S. state of Iowa, for example, selects high accident locations based on a combination of crashes per million miles traveled, crashes per mile per year, and value loss (crash severity).[47]

Fatality

The definition of a road-traffic fatality varies from country to country. In the United States, the definition used in the Fatality Analysis Reporting System (FARS)[48] run by the National Highway Traffic Safety Administration (NHTSA) is a person who dies within 30 days of a crash on a US public road involving a vehicle with an engine, the death being the result of the crash. In the U.S., therefore, if a driver has a non-fatal heart attack that leads to a road-traffic crash that causes death, that is a road-traffic fatality. However, if the heart attack causes death prior to the crash, then that is not a road-traffic fatality.

The definition of a road accident fatality can change with time in the same country. For example, fatality is defined in France as a person who dies in the 6 days (pre 2005) after the accident and was subsequently changed to the 30 days (post 2005) after the accident.[49]

History

The world’s first road traffic death involving a motor vehicle is alleged to have occurred on 31 August 1869.[51] An Irish scientist Mary Ward died when she fell out of her cousins' steam car and was run over by it.

The British road engineerJ. J. Leeming, compared the statistics for fatality rates in Great Britain, for transport-related incidents both before and after the introduction of the motor vehicle, for journeys, including those once by water that now are undertaken by motor vehicle:[12] For the period 1863–1870 there were: 470 fatalities per million of population (76 on railways, 143 on roads, 251 on water); for the period 1891–1900 the corresponding figures were: 348 (63, 107, 178); for the period 1931–1938: 403 (22, 311, 70) and for the year 1963: 325 (10, 278, 37).[12] Leeming concluded that the data showed that "travel accidents may even have been more frequent a century ago than they are now, at least for men".[12]

In 1969 a British road engineer compared the circumstances around road deaths as reported in various American states before the widespread introduction of 55 mph (89 km/h) speed limits and drunk-driving laws.[12]

'They took into account thirty factors which it was thought might affect the death rate. Among these were included the annual consumption of wine, of spirits and of malt beverages — taken individually — the amount spent on road maintenance, the minimum temperature, certain of the legal measures such as the amount spent on police, the number of police per 100,000 inhabitants, the follow-up programme on dangerous drivers, the quality of driver testing, and so on. The thirty factors were finally reduced to six on elimination of those which were found to have small or negligible effect. The final six were:

(a) The percentage of the total state highway mileage that is rural.

(b) The percent increase in motor vehicle registration.

(c) The extent of motor vehicle inspection.

(d) The percentage of state-administered highway that is surfaced.

(e) The average yearly minimum temperature.

(f) The income per capita.

'These are placed in descending order of importance. These six accounted for 70% of the variations in the rate.'

Society and culture

Economic costs

The global economic cost of MVCs was estimated at $518 billion per year in 2003 with $100 billion of that occurring in developing countries.[41] The Center for Disease Control and Prevention estimated the U.S. cost in 2000 at $230 billion.[52]

Legal consequences

In the United States, individuals involved in motor vehicle accidents can be held financially liable for the consequences of an accident, including property damage, injuries to passengers and drivers, and fatalities. Because these costs can easily exceed the annual income of the average driver, most US states require drivers to carry liability insurance to cover these potential costs. However, in the event of severe injuries or fatalities, victims may seek damages in civil court, often for well in excess of the value of insurance.

Additionally, drivers who are involved in a collision frequently receive one or more traffic citations, usually directly addressing any material violations such as speeding, failure to obey a traffic control device, or driving under the influence of drugs or alcohol. In the event of a fatality, a charge of vehicular homicide is occasionally prosecuted, especially in cases involving alcohol.

Convictions for traffic violations are usually penalized with fines, and for more severe offenses, the suspension or revocation of driving privileges. Convictions for alcohol offenses generally result in the revocation or long term suspension of the driver's license, and sometimes jail time and/or mandatory alcohol rehabilitation.

Due to increase in availability of cable news and Internet news, exposure to such legal actions has increased in recent years, specifically with coverage of cases and class action suits concerning SUV rollovers and recent incidents of sudden acceleration crashes highlighted by the 2010 Toyota Recall. Increased exposure has led to larger class action suits, and automobile owners' ability to link their collision causes and issues to ones in other regions has spread knowledge of external causes.

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